Description

Creates a prefix/ns context for the next XPath query. In particular, this is
helpful if the provider of the given XML document alters the namespace
prefixes. registerXPathNamespace will create a prefix for
the associated namespace, allowing one to access nodes in that namespace
without the need to change code to allow for the new prefixes dictated by the
provider.

Parameters

prefix

The namespace prefix to use in the XPath query for the namespace given in
ns.

ns

The namespace to use for the XPath query. This must match a namespace in
use by the XML document or the XPath query using
prefix will not return any results.

Notice how the XML document shown in the example sets a namespace with a
prefix of chap. Imagine that this document (or another
one like it) may have used a prefix of c in the past for
the same namespace. Since it has changed, the XPath query will no longer
return the proper results and the query will require modification. Using
registerXPathNamespace avoids future modification of the
query even if the provider changes the namespace prefix.